The present invention relates generally to storage systems and, more particularly, to storage management command control in a virtualized environment.
Storage Area Network (SAN) is becoming increasingly common in IT systems of business enterprises for realizing shared storage and high-speed and reliable data transfer. The connection between the storage and a host is typically carried out through Block Storage access of SCSI (Small Computer System Interface) according to Fibre Channel or iSCSI. In the SAN environment, storage management can be conducted in either in-band or out-of-band. In-band storage management uses the same data pass as general data transfer to transmit management commands from the hosts to the storage. In contrast, out-of-band storage management uses a physically and logically separate network to transmit command to and acquire management information from the storage.
In in-band management, a management command is transferred to the storage array as well as a generic data I/O to be written in the data storage device. The storage system has a dedicated storage volume for command transmission, often called the “Command Device.” The storage system treats the data written in specified storage volume as a management command.
Recently server virtualization technology is increasingly introduced into IT systems of business enterprises, and the SAN environment is considered as one of the prerequisites to construct a resilient and flexible virtualized system. Server virtualization is a technology that virtualizes a server computer by virtually splitting a set of computing resources (i.e., CPU, memory, storage, and other hardware devices) into multiple sets of computing resources so that it can run multiple operating systems and applications on one physical server. Each virtual computer running on the split resources is called a “virtual machine.” Examples of commercially available server virtualization technology include VMware ESX Server, Microsoft Hyper-V, and Citlix XenServer.
The virtual machine can leverage both a virtual device and a physical device. The virtual device is stored as one or multiple sets of files which are used as a virtual hard disk for the virtual machine. Generally, not the file system on the virtual machine but the server virtualization software or file system on which the server virtualization software runs manages the actual storage device that stores virtual hard disk files. A virtual SCSI command issued form within the virtual machine is once transferred to the server virtualization software or the aforementioned file system and converted to the actual SCSI command to be sent to the storage system. Furthermore, multiple virtual machines can share one storage volume and a block-accessed storage system is generally not aware of the virtual hard disk files.
On the other hand, the physical device is used directly by the virtual machine. In this case, the physical disk/volume is assigned and mounted to the virtual machine as a storage device for the virtual machine and it is not interposed by other file systems. Therefore, a SCSI command issued from within the virtual machine is transferred almost directly to the storage without conversion.
In the existing technology, in-band storage management requires that the physical device be mounted to the virtual machine when managing storage from the virtual machine because the storage needs to be aware which volume is the command device. If it is a virtual device, block-accessed storage system is not able to recognize that a management command is written. Consequently, the number of storage volumes to be managed increases because of the storage system management constraint, whereas virtualization technology enables resource consolidation that simplifies the system management process.